Georg Schreckenbach

The readily accessed 1,7-dibrominated derivative of 2,3,5,6-tetramethyl-BODIPY is shown to be an effective precursor to a derivative appended with acetylide −C≡CH groups at these positions, through the intermediacy of the trimethylsilyl-protected compound (−C≡C–SiMe3). The acetylide functionality can in turn be metalated with dicobalt-hexacarbonyl clusters, or incorporated into 1,2,3-triazole rings through reaction with in situ generated propyl azide. The resulting new compounds have been structurally characterized by X-ray crystallography. Their electrochemical and optical spectroscopic properties are described and interpreted with the aid of time-dependent density functional theory (TD-DFT) calculations. The acetylide and the triazole derivative are intensely fluorescent in organic solvents at ambient temperature. Bis-N-methylation of the triazole gives a bis-triazolium salt that is soluble in water, while retaining a very high fluorescence quantum yield. On the other hand, the Co2(CO)6 appendages completely quench the fluorescence of the BODIPY moiety, likely through efficient intramolecular energy transfer, an interpretation supported by the spectral overlap of the absorption and emission of the respective units.

A comprehensive evaluation of constricted variational density functional theory (CV-DFT) is presented for intra- and intermolecular singlet–singlet excitations with varying degrees of charge transfer (CT) to understand the role of virtual orbitals in variational calculations of the excited state. The effect of initial guess (TDDFT, sTDDFT, or TDDFT+TB) is investigated to assess the robustness of CV-DFT for these excitations. Mild states (dCT ≤ 1.50 Å) do not require variational calculations, whereas strong states (dCT ≥ 1.50 Å) benefit from CV-DFT calculations. Strong CT states demonstrating charge transfer over intermediate distances (1.50 Å ≤ dCT ≤ 2.50 Å) require a self-consistent optimization of the natural transition orbitals (NTOs) for the excitation. In such cases, the SCF-CV(∞)-DFT scheme (and additional orbital relaxation) efficiently captures missing NTOs compared to the linear response regime, as well as yielding improved excitation energies. In calculations employing LDA and PBE, the SCF-CV(∞)-DFT scheme yields excitation energies with root mean squared error (RMSE) of 0.63 eV, whereas, with hybrid functionals, the RMSE is reduced to ≈ 0.33 eV against ab initio data. The RMSE with PBE0 is 0.23 eV and is comparable to double-hybrid TDDFT results in the literature. However, for fully charge-separated states (dCT ≥ 2.50 Å), the SCF-CV(∞)-DFT scheme collapses to a charge-localized state as it is deemed variationally unstable. For these states, a variational calculation wherein the NTOs are frozen at their initial guess in the single-orbital replacement (SOR)-R-CV(∞)-DFT scheme removes the variational instability, yielding excellent agreement with theoretical best estimates for both intramolecular and intermolecular CT excitations. These findings show that variational ΔSCF calculations of excited states can be achieved with CV-DFT by optimizing and relaxing higher-lying virtual orbitals.

Novel La–[ ^18/19 F]fluoride complexes lay a foundation towards ¹⁸ F/ ²²⁵ Ac/La theranostics. Systematic evaluation of La–F coordination chemistry reveals a fundamental trade-off: ligand electronics govern La–F bond strength and stability.

Ce embedded chalcogenide system achieves the highest CO ₂ RR efficiency, due to 4f-electron localization, which enhances π-backdonation and Pauli repulsion, thereby facilitating CO desorption and accelerating the catalytic cycle.

Octacoordinate ammine complexes of electropositive metals (M[NH ₃ ] ₈ , M = Ca, Sr, Ba, Eu, Yb) maintain full ligand saturation and robust structural integrity across gas, liquid, and solid phases, challenging conventional coordination theory. Using a multiscale quantum chemical framework, we show that their stability originates from superatomic shell closure. In the gas phase, an 18-electron configuration (1S ² 1P ⁶ 1D ⁸ 2S ² ) formed by metal-ligand hybridized orbitals ensures closed-shell stability independent of d -orbital participation. Upon solvation, the system adapts to a 16-electron configuration (1S ² 1P ⁶ 1D ⁸ ), preserving the superatomic hierarchy through orbital reorganization. In the crystalline state, these orbitals propagate into delocalized bands, enabling a seamless transition from molecular to bulk coordination behavior. These findings define a phase-independent coordination paradigm based on electronic shell closure and expand the applicability of superatomic models to weak-field and non-classical complexes.

In this paper, we present the Amsterdam Modeling Suite (AMS), a comprehensive software platform designed to support advanced molecular and materials simulations across a wide range of chemical and physical systems. AMS integrates cutting-edge quantum chemical methods, including Density Functional Theory (DFT) and time-dependent DFT, with molecular mechanics, fluid thermodynamics, machine learning techniques, and more, to enable multi-scale modeling of complex chemical systems. Its design philosophy allows for seamless coupling between components, facilitating simulations that range from small molecules to complex biomolecular and solid-state systems, making it a versatile tool for tackling interdisciplinary challenges, both in industry and in academia. The suite also emphasizes user accessibility, with an intuitive graphical interface, extensive scripting capabilities, and compatibility with high-performance computing environments.

This study combines computational and experimental methods to investigate how auxiliary ligands enhance thermodynamic stability in hexacoordinate ⁸⁹Zr–DFO (deferoxamine) complexes.